The proposed research has three objectives. The first is aimed at understanding the postnatal development of the lateral geniculate nucleus (LGN) in the cat. Light and electron microscopic methods will be used to investigate the maturation of LGN neurons, and the synaptic relations which they form. The second objective is to assess the influence of partial and complete visual deprivation on the normal sequence of LGN development, and to determine if there exists a specific developmental period during which the effects of deprivation are particularly severe. Our previous work has demonstrated that after neonatal monocular enucleation, new retinogeniculate connections are formed by axons from the intact eye. Therefore the third objective is to determine with the electron microscope whether these new connections are synaptically competent, and to investigate with the Golgi method whether LGN cells that are deafferented at birth modify the spatial organization of their dendritic tree.